One form of a stimulus imparting device disclosed in Patent Literature 1 has been known. As indicated in FIG. 2 of the Patent literature 1, the stimulus imparting device includes a dangerous state detecting means including a lane departing predicting/detecting means and/or a driver dozing state detecting means for vehicle and a motor control means for warning which generates a warning vibration at an electric seat by rotating a motor which operates the electric seat in positive and reverse directions by outputting a positive or reverse rotation instruction signal upon receipt of a detecting signal from the dangerous state detecting means. According to this structure, a warning by vibration to the driver can be made by utilizing a motor which is provided in advance for operating each portion of the electric seat.
Further, another form of the stimulus imparting device disclosed in Patent literature 2 has been known. As indicated in FIG. 1 of the Patent Literature 2, the stimulus imparting device is configured so that the airbag 3 expands and imparts the pressure sensitive awakening stimulus to the spinal erectors of the driver D, when the driver D, who is the subject driver of the device, becomes drowsy. The stimulus imparting device is configured so that a physiological measurement device 8 measures a muscle potential, as a parameter indicating a state of activity of the spinal erectors. The stimulus imparting device is configured so that an awakening maintaining ECU (Electronic Control Unit) 11 controls the strength of a pressure sensitive awakening stimulus imparted to spinal erectors to an appropriate strength which can activate brain cells of a driver D, based on a measured muscle potential. In addition, the stimulus imparting device is structured so that the vibration body 7 imparts the vibration stimulus to the spinal erectors. As a result, the drowsy driver D can be effectively returned to an awakening state.